Another collimation thread

[wookie1965]

I have done the Astrosheds tweak with the steel and PTFE washer on the first picture everything looks ok,  but as you can see once through the Cheshire dowsnt quite look right any advice welcome please.

[Beulah]

First of all, is the Cheshire seated in the holder properly and the focuser wound all the way down?

I'd say the secondary needs shifting a wee tad to the left and down and then tweak the primary (looking at the second image).

It doesn't need to be tweaked that much...it depends which image you have posted here looks the most accurate to your eye. Third images renders the secondary more off centre than the second.

[wookie1965]

I thought that when i looked on here could see better take a look at this one now see what you think.

[Beulah]

Still think that the secondary needs moving veeeeerrry slightly left and down. The primary is very nearly there too. You might find that the secondary adjustment might sort that out.

Trouble is, those tiny secondary tweaks can turn into large ones and you have to start all over again!!!  The air often turns blue when that happens to me.

[wookie1965]

Left and down now can that be accomplished with the three collimation screws or am i going have to turn the middle screw say a quarter turn and thank you.

[Scooot]

Try rotating the secondary around the central bolt a tiny bit and you'll probably find it will centre your cheshire in the view. (If you turn it the right way).

[wookie1965]

It seems my vanees were a little out and rotation was think ive got it now looks alot better dont know if this photo shows it as good as it looks through the Cheshire.

[wookie1965]

That secondary still looks a tad out looks ok through the Cheshire but once get the picture on here and can see it blown up can see its out going have another go at it tomorrow getting frustrated now.

[Beulah]

Right. From that last photo, looks like you are nearly there. Tweak the primary very slightly so that centre dot is directly behind the intersection and you are off. 

[Moonshane]

I agree. much closer and if your secondary is rounded and centrered to the drawtube you are in business. primary is simple.

[Scooot]

It doesn't look too bad. What I'd do is block the primary out with a piece of card and then look through the cheshire to see if the secondary its central, ie so you can see an equal amount of the secondary inside the view of the cheshire and its crosshairs are in the middle. If it's not,rotate it until it is. Then with the card removed check you can see the mirror clips. It can be frustrating as you've discovered -

[wookie1965]

Ive done this a few times normally get it easy for some reason this time, i wondering if the 1mm steel washer and the 1mm PTFE washer is not giving me enough room to adjust the secondary that bit to get it just right. I will have another go in morning and post a picture thank you all.

[Moonshane]

I did find it difficult to get the secondary right when I collimated your scope. I personally don't like Teflon and steel and prefer a disc or two cut from the side of a plastic milk bottle.

[wookie1965]

Shane i think your right im going to try with just the PTFE washer tomorrow see if that makes any difference if not i will go back to the two washers cut out of the milk bottle.

[wookie1965]

Took a picture just through focuser show mirror centralised and round then through Cheshire, this looks like the mirror is a bit to one side must be the angle the camera was but looks better see what you think.

[wookie1965]

Had another go think ive got it now

[wookie1965]

Now this looks more like it i hope only been doing it 3 hours

[glynnlondon]

Better than my effort Im having a mare. My secondary is all over the shop.  Oh well back to the start again with astro baby.

[wookie1965]

Better than my effort Im having a mare. My secondary is all over the shop.  Oh well back to the start again with astro baby.

http://www.schlatter.org/Dad/Astronomy/collimate.htm

Use this as well i did and just take your time took me 3 hours normally only takes 10 minutes, just had nightmare this time but persevere.

[glynnlondon]

Thanks wookie will go again after work tomorrow. Onwards and upwards  .

[wookie1965]

Did a star test a saw something very similar to this i dont think it looks right but i dont have a clue whats wrong i cant work out what the cut out bit is in the circle. I looked at the moon and the craters looked pin sharp and the circles look the same unfocused on the Star just dont know what that bit is thats missing.

[wookie1965]

Is it my focuser intruding into the light path and will that have any bearing on my views.

[Jason D]

Yes, most likely it is you focuser intruding. Try to defocus by racking out the focuser.

I am not sure what you are trying to accomplish by star testing! Are you evaluating the optics or checking collimation?

Regardless, you are doing it the wrong way. To star test you need to be at high magnification and defocus enough to see few rings (2 to 4 rings)

Jason

[wookie1965]

Yes, most likely it is you focuser intruding. Try to defocus by racking out the focuser.

I am not sure what you are trying to accomplish by star testing! Are you evaluating the optics or checking collimation?

Regardless, you are doing it the wrong way. To star test you need to be at high magnification and defocus enough to see few rings (2 to 4 rings)

Jason

150p 4mm then and yes collimation thank you.